User equipment, nodes and methods performed therein

ABSTRACT

A method performed by a user equipment, UE, for handling communication in a wireless communication network, providing dual connectivity, DC, communication through a master node using a master cell group, MCG, over a first radio interface between the UE and the master node and through a secondary node using a secondary cell group, SCG, over a second radio interface between the UE and the secondary node. The UE detects a failure associated with the SCG and suspends actions associated with the SCG. The UE further performs a reconfiguration of the SCG in case the UE has received a MCG radio resource control, RRC, message comprising SCG configuration, wherein performing the reconfiguration of SCG comprises applying the reconfiguration; and resuming or not resuming the actions associated with the suspended SCG.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/276,362, filed Feb. 14, 2019, which is a continuation ofInternational Application No. PCT/SE2018/051061, filed Oct. 18, 2018,which claims the benefit of U.S. Provisional Application No. 62/584,158,filed on Nov. 10, 2017, the entireties of all of which are Xorporatedherein by reference.

FIELD

Embodiments herein relate to a user equipment, a master node, asecondary node and methods performed therein for communication. Inparticular embodiments herein relate handle communication in a wirelessnetwork e.g. for avoiding race conditions during Secondary Cell Group(SCG) failure handling.

BACKGROUND

Generally, all terms used herein are to be interpreted according totheir ordinary meaning in the relevant technical field, unless adifferent meaning is clearly given and/or is implied from the context inwhich it is used. All references to a/an/the element, apparatus,component, means, step, etc. are to be interpreted openly as referringto at least one instance of the element, apparatus, component, means,step, etc., unless explicitly stated otherwise. The steps of any methodsdisclosed herein do not have to be performed in the exact orderdisclosed, unless a step is explicitly described as following orpreceding another step and/or where it is implicit that a step mustfollow or precede another step. Any feature of any of the embodimentsdisclosed herein may be applied to any other embodiment, whereverappropriate. Likewise, any advantage of any of the embodiments may applyto any other embodiments, and vice versa. Other objectives, features andadvantages of the enclosed embodiments will be apparent from thefollowing description.

In LTE, the Radio Resource Control (RRC) protocol is used toconfigure/setup and maintain the radio connection between a userequipment (UE) and a network node such as an evolved NodeB (eNB). Whenthe UE receives an RRC message from the eNB, it will apply theconfiguration (the term “compile” may also be used to refer to theapplication of the configuration), and if this succeeds the UE generatesan RRC complete message that indicates a transaction identity (ID) ofthe RRC message that triggered this response.

Since LTE-release 8, three Signalling Radio Bearers (SRBs), namely SRB0,SRB1 and SRB2 have been available for the transport of RRC and NonAccess Stratum (NAS) messages between the UE and eNB. A new SRB, knownas SRB1bis, was also introduced in rel-13 for supporting Data Over NAS(DoNAS) in Narrowband-Internet of things (NB-IoT).

SRB0 is for RRC messages using a Common Control Channel (CCCH) logicalchannel, and it is used for handling RRC connection setup, RRCconnection resume and RRC connection re-establishment. Once the UE isconnected to the eNB, i.e. RRC connection setup or RRC connectionreestablishment/resume has succeeded, SRB1 is used for handling RRCmessages, which may include a piggybacked NAS message, as well as forNAS messages prior to the establishment of SRB2, all using a DedicatedControl Channel (DCCH) logical channel.

SRB2 is for RRC messages which include logged measurement information aswell as for NAS messages, all using DCCH logical channel. SRB2 has alower priority than SRB1, because logged measurement information and NASmessages may be lengthy and may cause the blocking of more urgent andsmaller SRB1 messages. SRB2 is always configured by Evolved-UMTSTerrestrial Radio Access Network (E-UTRAN) after security activation.

E-UTRAN supports Dual Connectivity (DC) operation whereby a multipleReception/Transmission (Rx/Tx) UE in RRC_CONNECTED mode is configured toutilize radio resources provided by two distinct schedulers, located intwo eNBs, i.e. radio base stations, connected via a non-ideal backhaulover the X2 interface, see 3GPP 36.300 v. 13.0.0. “Non-ideal backhaul”implies that the transport of messages over the X2 interface between thenetwork nodes may be subject to both packet delays and losses.

eNBs involved in DC for a certain UE may assume two different roles: aneNB may either act as a Master Node (MN), also referred to as Master eNB(MeNB), or as a Secondary Node (SN), also referred to as Secondary eNB(SeNB). In DC a UE is connected to one MN and one SN.

In LTE DC, the radio protocol architecture that a particular bearer usesdepends on how the bearer is setup. Three bearer types exist: MasterCell Group (MCG) bearer, Secondary Cell Group (SCG) bearer and splitbearers. RRC is located in the MN and SRBs are always configured as MCGbearer type and therefore only use the radio resources of the MN. When anode acts as an SN, the LTE DC solution does not have any UE RRC contextof that UE and all such signalling is handled by the MN. FIG. 1 shows aLTE DC User Plane (UP) architecture.

In 3GPP, a study item on a new radio interface for 5G has recently beencompleted and 3GPP has now continued with the effort to standardize thisnew radio interface, often abbreviated by New Radio (NR).

LTE-NR DC, also referred to as LTE-NR tight interworking, is currentlybeing discussed for rel-15.

In this context, the major changes from LTE DC are

-   -   The introduction of a split bearer from the SN known as SCG        split bearer. The SN in this case is also referred to as SgNB,        secondary gNB, where gNB denotes an NR base station.    -   The introduction of split bearers for RRC.    -   The introduction of a direct RRC from the SN known as SCG-SRB or        direct SRB.

FIGS. 2 to 4 show the User Plane (UP) and Control Plane (CP)architectures for LTE-NR tight interworking.

It should be appreciated that embodiments herein apply to differentscenarios where the MN and SN nodes can apply various radio interfacetechnologies. The MN node can apply e.g. LTE or NR, and the SN node canalso use either LTE or NR without departing from the main concept ofembodiments herein. Other technologies could also be used over the radiointerface. The 3GPP technical report TR 38.304 v. 0.0.3 includes variousscenarios and combinations where the MN and SN are applying either NR,LTE or both.

For the first phase of 5G standardization and 5G deployment, the mostlikely scenario is that MN will apply LTE, and the SN will apply the newradio interface, denoted NR, currently being under standardization.Thus, we focus on this scenario and use the term MeNB and SgNB for therest of this description.

The following terminologies are used throughout this text todifferentiate different dual connectivity scenarios:

-   -   DC: LTE DC, i.e. both MN and SN employ LTE.    -   EN-DC: LTE-NR dual connectivity where LTE is the master and NR        is the secondary.    -   NE-DC: LTE-NR dual connectivity where NR is the master and LTE        is the secondary.    -   NR-DC (or NR-NR DC): both MN and SN employ NR.    -   Multi-RAT DC (MR-DC): a generic term to describe where the MN        and SN employ different radio access technologies (RAT). EN-DC        and NE-DC are two different example cases of MR-DC.

As already mentioned above, the DC approach introduced for 5Gstandardization includes a solution for split bearers for SRBs, seeFIGS. 3 and 4. The intent of introducing such “RRC diversity” is toenable e.g. better mobility robustness and improved message deliverybetween the infrastructure and the UE. For example, it is then possibleto send a handover message or any other reconfiguration message over thebest link, even if one of either the link or links to the MeNB (or SgNB)has deteriorated significantly. It is also possible to send duplicatesof the same message over both MeNB and SgNB to achieve a bettersuccess-rate and faster delivery of the concerned message; in case thelinks are error prone. Such benefits of “RRC diversity” are notavailable in the current LTE DC solution, and 3GPP has thereforeundertaken the challenge to enable such RRC diversity. Having RRCdiversity may prove particularly important for ultra-reliableconnections with low latency, often called Ultra Reliable Low LatencyCommunication (URLLC).

As can be seen in FIG. 4, RRC messages generated and/or transmitted fromthe MN can be sent either via the MeNB, or relayed over an X2 interfaceto the SgNB. The messages received over the different paths in the UEare then combined to the LTE Packet Data Convergence Protocol (PDCP) andthen forwarded to the LTE RRC receiving entity and processed further. Inthe uplink, the UE generates LTE RRC messages that the UE may transmiteither over the NR radio interface towards the SgNB or via the MN nodeusing LTE technology. Messages received in the SgNB are then forwardedover an X2 interface towards the MeNB node.

One of the main reasons behind the introduction of SCG SRB between theUE and SN is that there may be SCG reconfiguration scenarios where SNcan configure the UE directly without the need for coordination with theMN. This is for cases such as intra-SN mobility, measurementconfigurations/reporting related to the intra-SN cells, etc. Intra-SNmeaning within SNs. Thus, it has been agreed in 3GPP that SCG SRB willsupport a (subset) of the functionalities, namely:RRCConnectionReconfiguration, in the DL; andRRCConnectionReconfigurationComplete and MeasurementReport in the UL.

Another control signalling mechanism, in addition to SCG SRB and splitSRBs, in LTE-NR tight interworking is using embedded RRC and is alsoillustrated in FIG. 4. Embedded RRC is employed for two cases:

-   -   1. When SCG SRB is not available.    -   2. The UE has to be configured with settings that affect both        the NR and LTE legs, i.e. a co-ordination is required, even if        direct SRB is available.

For the first case, the SgNB sends the RRC message to the MeNB via theX2 interface, which the MeNB then embeds in its own RRC message andsends via SRB1, which could be split or not. The UE then extracts theembedded NR RRC message from the container MeNB RRC message and applythe configurations on the NR leg. In the UL direction, the UE embeds theNR RRC messages in an LTE RRC message towards the MeNB, and the MeNBwill extract the embedded NR RRC message from this and forwards it tothe SgNB.

For the second case, i.e. messages/configurations that requireco-ordination between the MeNB and SgNB, e.g. inter (i.e. betweendifferent)-RAT measurement configurations, settings affecting buffersizes which the UE has to allocate to the NR and LTE legs withoutexceeding the total buffering capability of the UE, etc., the SgNB nodecan send the NR configurations, the MeNB and SgNB can negotiate thefinal configurations since it affects the settings of both legs, and thefinal configuration for the NR leg is sent to the UE via an LTE RRCmessage that contains the embedded NR RRC message, wherein the finalembedded NR RRC message still being generated by the SN.

In LTE, a UE considers a radio link failure (RLF) to be detected when:

-   -   i. Upon detecting a certain number of out of sync (OOS)        indications from the lower layers associated with a Primary Cell        (PCell) within a given time, or    -   ii. upon random access problem indication from Media Access        Control (MAC), or    -   iii. upon indication from Radio Link Control (RLC) that the        maximum number of retransmissions has been reached for an SRB or        for a data radio bearer (DRB).

When RLF is detected, the UE prepares an RLF report, which includes,among other information, the measurement status of the serving andneighbour cells at the moment when RLF was detected, goes to IDLE mode,selects a cell following IDLE mode cell selection procedure wherein theselected cell could be the same serving node/cell or another node/cell,and starts the RRC re-establishment procedure, with a cause value set torlf-cause.

In the case of LTE DC, the RLF detection procedure is similar to whatwas described above except that for (i), we are concerned only the PCellof the MN, the MAC in (ii) is the MCG MAC entity and the RLC in (iii) isthe MCG RLC and the DRB in (iii) corresponds to MCG and MCG-split DRBs.

On the other hand, failure on the secondary side, known as SCGFailure,is detected by:

-   -   a) upon detecting radio link failure for the SCG, in accordance        with i,ii and iii above, i.e.

replace PCell for primary secondary cell (PSCell), MCG MAC for SCG MAC,and MCG/MCG-Split DRB for SCG DRB, or

-   -   b) upon SCG change failure, i.e. not able to finalize SCG change        within a certain duration after the reception of an RRC        connection reconfiguration message instructing the UE to do so,        or    -   c) upon stopping uplink transmission towards the PSCell due to        exceeding the maximum uplink transmission timing difference when        powerControlMode is configured to 1.

Upon detecting SCGFailure, the UE sends an SCGFailureInformation messagetowards the MN, which also includes measurement reports, and the MN caneither release the SN, change the SN/Cell, or reconfigure the SCG. Thus,a failure on the SCG will not lead to a re-establishment to be performedon the MCG.

3GPP has agreed to adopt the same principles in the context of LTE-NRinterworking, i.e. re-establishment in the case of RLF on the master legand recovery via SCGFailureInformation and SNrelease/change/modification in case of RLF on the secondary leg.Specifically, it has been agreed:

-   Upon SgNB failures, UE shall:    -   Suspend all SCG DRBs and suspend SCG transmission for MCG split        DRBs, and SCG split DRBs;    -   Suspend direct SCG SRB and SCG transmission for MCG split SRB;    -   Reset SCG-MAC;    -   Send a SCGFailureInformation message to the MeNB with        corresponding cause values.

The problem with the existing solution is in the case the SCG failure inthe UE occurs at the same time there is an ongoing SCG reconfigurationfrom the SN. This can result in two types of problems:

-   1. When should the UE resume the SCG link which is suspended at the    detection of SCG failure.-   2. What is the last valid UE configuration according to the UE and    network.    -   If the network and UE does not have an agreement on the last        valid UE configuration the network is forced at the next        reconfiguration to send the full UE configuration which may be a        very large message.    -   If the network and UE do have an agreement on the last valid UE        configuration the network can at the next reconfiguration use        delta signalling, which is in comparison with the valid UE        configuration, which is more efficient.

Embodiments herein are related to the case when SCG SRB is notconfigured and all SN RRC messages are delivered embedded with the MCGSRB, or the case where SCG SRB is configured and the last SCGreconfiguration that was sent to the UE just before SCG failure was sentvia embedded RRC, e.g. due to a need for co-ordination with the MCG, orvia the SCG SRB.

Consider a situation where the UE has SCG_configuration_version1, andthe SN has sent SCG_configuration_version2 via embedded SRB.Furthermore, an SCG failure is detected at the UE, e.g. due to RLF onthe PSCell, due to max number of RLC retransmissions on an SCG DRB, etc.

Case 1: The MN receives the SCGFailureInformation before it has managedto send the MCG RRC message that embeds the SCG_configuration_version2to the UE.

Case 2: The MN has started sending the MCG RRC message that embeds theSCG_configuration_version2 to the UE when it receives theSCGFailureInformation, but it has not finalized it yet, e.g. part of themessage was still not scheduled, part of the message was beingre-transmitted due to lower layer issues)

Case 3: The MN has successfully sent the MCG RRC message that embeds theSCG_configuration_version2 to the UE but while waiting for the completemessage for that configuration, an SCG failure was detected in the UE.

Case 3 a: while the UE was still applying theSCG_configuration_version2.

Case 3 b: the UE has applied the SCG_configuration_version2, and hassent the complete message to the SN embedded with an uplink (UL) messageto the MN, but the message has not been received at the MN yet.

Case 3 c: same as case 3 b, but the MN has received the UL message fromthe UE, but has not delivered the lower layer acknowledgement (ACK),i.e. the UE still not sure if the message has been delivered to the MN.

In all cases, a situation may arise where the SN and the UE might havedifferent SCG configurations. That is, when the MN tries to get the UE'sSCG configuration from the SN, the SN will not be sure to provideSCG_configuration_version1 or SCG_configuration_version2. The SN willnot know whether the UE has applied the SCG_configuration_version2 ornot as it has not received the complete message.

In case 1, if the MN refrains from forwarding theSCG_configuration_version2, since it knows that the UE has experiencedSCG failure, the configuration of the UE will remainSCG_configuration_version1.

On the other hand, if the MN forwards the SCG_configuration_version2anyways to the UE, the UE will try to apply the configuration. In LTEDC, such a reception of a reconfiguration would have been interpreted bythe UE as a response by the network to the SCG failure that it has sentearlier. In this case the UE may decide to resume the SCG link which istypically suspended at SCG failure. But since this message was generatedby the SN before the SCG failure was detected/reported, there may not bemobilityControlInfoSCG (for SCG change) or release indicator (SCGrelease) meaning it is unlikely that the resume of SCG link would worksince UE is still in the same SCG cell. However, ifSCG_configuration_version2 was a mobility configuration from the SN,e.g. change of the PScell, then this could also be mistaken by the UE asa response for the SCGFailure Report that has just been sent. Themobility command from the SN might have actually solved the SCG issue,but since the MN is not aware of it, it will try to handle the SCGfailure. This might result in:

-   -   Unnecessary signalling: If the MN decides to keep the SN, then        it may forward the measurement results to the SN, along with an        SgNB modification request, for example, or in a separate        message, which will probably result in no actual modification        from the SN as the SN knows that it has just applied the        mobility.    -   Unnecessary SN change or release: The MN may decide to change        the SN, even if the UE has actually successfully recovered the        SCG, e.g. changed the PScell. The situation is the same in case        the MN decides to release the SN if there was no other SN with a        better signal quality.

The situation in case 2 is the same as in case 1, i.e. the UE has notreceived the reconfiguration message yet, so all the above considerationfor case 1 still applies.

In case 3, regardless of the UE's state (i.e. case 3 a, 3 b, 3 c), it isnot completely clear also what the UE behavior will be. But assuming aproper UE implementation, we can assume that the UE will not interruptthe ongoing application of the configuration if SCG failure happens.Thus, cases 3 a and 3 b are effectively the same. And from the UE'spoint of view, case 3 c is also similar to case 3 a and 3 b in that itis not sure whether the complete message was received at the MN or not.However, from the network's point of view, case 3 b and 3 c aredifferent because in case 3 c, the network knows the UE has applied thelatest configurations. Since both the SCG failure information as well asthe complete message are sent via SRB1, even in case 3 a/3 b, the SCGfailure information will be scheduled/sent after the complete message.As such, the network and the UE has the same configuration, e.g.SCG_configuration_version2, but the SN is not yet aware of it since theMN has not forwarded the complete message to the SN yet. and also likein cases 1 and 2, that this latest reconfiguration might have alreadyresolved the SCG failure but the MN is not aware of it and thus will tryto resolve a problem that is already taken care of.

The last SCG reconfiguration may be sent via embedded SRB, but also sentvia SCG SRB.

Case 4: The SCG_configuration_version2 was sent via the SCG SRB

Case 4 a: the UE did not receive the SCG_configuration_version2 due tothe SCG failure.

Case 4 b: the UE has received the reconfiguration message with theSCG_configuration_version2, but it has not managed to send the completemessage for that

In case 4, the problem is that the SN node does not know if the UE hasapplied the SCG_configuration_version2 or not.

In R2-1710622 “Further details on SRB3 handling” by Intel Corporation itwas proposed that the UE should include a transaction identity (ID), inthe SCG Failure message, of the last RRC SCG configuration that it gotprior to the failure. And the MN may include this information whenrequesting the latest SCG configuration from the SN. In this way, atleast the network will know which configuration the UE considers validat the time of SCG failure. However, there are still issues with thissolution:

-   -   The SCGFailure reporting and the forwarding of the embedded        SCG_configuration_version2 may happen at the same time, e.g.        during a same Transmission Time Interval (TTI). Thus, there is        still a chance that the UE will have received the latest        configuration but has indicated the previous configuration in        the SCG Failure.    -   If the embedded SCG_configuration_version2 has not been sent        before the SCGFailure report was received at the MN, then the MN        may discard this message and request the latest SCG        configuration from the SN (indicating the previous transaction        ID). This will have the same downside as described above, i.e.        the MN trying to handle the problem that is already solved by        the SN.    -   The solution requires the UE to keep track of SCG configuration        transaction IDs even after the configurations has been applied        successfully, just in case a failure happens during the next        reconfiguration.

Thus, there is still an issue for coordinating which SCG configurationis used at the UE.

SUMMARY

Certain aspects of the embodiments may provide solutions to one or moreof the challenges above or other challenges.

An object herein is to provide a mechanism for efficiently handlingcommunication of a UE being connected to a master node and a secondarynode in a wireless communication network.

According to an aspect the object is achieved by providing a methodperformed by a UE for handling communication in a wireless communicationnetwork providing dual connectivity (DC) communication through a masternode using a MCG over a first radio interface between the UE and themaster node and through a secondary node using a SCG over a second radiointerface between the UE and the secondary node. The UE detects afailure associated with the SCG and suspends actions associated with theSCG. The UE performs a reconfiguration of the SCG upon reception of anMCG RRC message comprising SCG configuration, wherein performing thereconfiguration of SCG comprises applying the reconfiguration; andresuming or not resuming the suspended actions associated with the SCG.

According to another aspect the object is achieved by providing a methodperformed by a master node for handling communication in a wirelesscommunication network, wherein the master node is configured to operatein cooperation with a secondary node to provide DC communication with auser equipment through the master node using a MCG over a first radiointerface between the UE and the master node and through the secondarynode using a SCG over a second radio interface between the UE and thesecondary node. The MN receives from the UE, an indication indicating afailure associated with the SCG. The MN then handles the failure basedon whether one or more conditions are fulfilled, and wherein handlingthe failure comprises performing one or more of: postponing handling ofthe failure; performing a reconfiguration to the SCG; ignoring thefailure; moving the UE to a different secondary node; providing thesecondary node with a reconfiguration response message.

According to yet another aspect the object is achieved by providing amethod performed by a secondary node for handling communication of a UEin a wireless communication network, wherein the secondary node isconfigured to operate in cooperation with a master node to provide DCcommunication with the UE through the secondary node using a SCG over asecond radio interface between the UE and the secondary node and themaster node using a MCG over a first radio interface between the UE andthe master node. The SN transmits to the UE, an SCG reconfigurationmessage that includes a mobility flag wherein the mobility flag is setto true when the reconfiguration concerns mobility within the secondarynode and the mobility flag set to false or not included when thereconfiguration is not concerned with mobility within the secondary node

According to still another aspect the object is achieved by providing aUE for handling communication, e.g. handling reconfiguration orperforming the reconfiguration, in a wireless communication networkproviding DC communication through a MN using a MCG over a first radiointerface between the UE and the MN and through a secondary node using aSCG over a second radio interface between the UE and the secondary node.The UE is configured to detect a failure associated with the SCG such asa SCG failure, and to suspend actions associated with the SCG. The UE isfurther configured to perform a reconfiguration of the SCG uponreception of an MCG RRC message comprising SCG configuration, by beingconfigured to apply the reconfiguration; and resume or not resume thesuspended actions associated with the SCG.

According to yet still another aspect the object is achieved byproviding a master node for handling communication in a wirelesscommunication network, wherein the master node is configured to operatein cooperation with a secondary node to provide DC communication with aUE through the master node using a MCG over a first radio interfacebetween the UE and the master node and through the secondary node usinga SCG, over a second radio interface between the UE and the secondarynode. The master node is configured to receive from the UE an indicationindicating a failure associated with the SCG. The master node is furtherconfigured to handle the failure based on whether one or more conditionsare fulfilled, and wherein handle the failure comprises performing oneor more of: postponing handling of the failure; performing areconfiguration to the SCG; ignoring the failure; moving the UE to adifferent secondary node; providing the secondary node with the areconfiguration response message.

According to another aspect the object is achieved by providing asecondary node for handling communication of a UE in a wirelesscommunication network, wherein the secondary node is configured tooperate in cooperation with a master node to provide DC communicationwith the UE through the secondary node using a SCG over a second radiointerface between the UE and the secondary node and the master nodeusing a MCG over a first radio interface between the UE and the masternode. The secondary node is configured to transmit to the UE, an SCGreconfiguration message that includes a mobility flag wherein themobility flag is set to true when the reconfiguration concerns mobilitywithin the secondary node and the mobility flag set to false or notincluded when the reconfiguration is not concerned with mobility withinthe secondary node.

Embodiments introduce mechanisms to avoid race conditions andunnecessary reconfigurations during SCG failure recovery in e.g. dualconnectivity of different RATs such as EN-DC, where the last SCGreconfiguration message was sent from the SN to the UE e.g. embeddedwithin an MN RRC message or over SCG SRB. This is done by definingspecific behavior in the UE for when e.g. the UE should resume the SCGlink based on e.g. the presence of mobility information in the SCGconfiguration or an explicit indication that the SCG link should beresumed.

Additionally, mechanisms are introduced to ensure that the MN node knowsif the UE has resumed the SCG link or not. This is done by letting theSN indicate to the MN if an embedded SN RRC message is related tomobility, and in this case, the MN will not try to handle the SCGfailure (since the SN mobility information may solve the SCG failure)and cause unnecessary signalling/reconfigurations. Embodiments hereinmay ensure that the SCG failure conditions are resolved properly in theUE. Embodiments herein may further ensure that the UE and RAN RRCcontext is synchronized or re-synchronized after failure.

As an addition or an alternative to previous embodiments, the UE mayindicate to the MN in a response message to an RRC reconfiguration(containing SCG configuration) if the UE has resumed the SCG link. Thisenables the MN to ignore the previous SCG failure.

Additionally, mechanisms are introduced making it possible to ensurethat the UE has applied the latest SCG reconfiguration that wasgenerated by the SN before the failure was detected by the UE, and alsothat the complete message is received at the SN. This enables the use ofmore efficient delta signalling at the next reconfiguration.

Certain embodiments may provide one or more of the following technicaladvantage(s). Embodiments ensure that SCG failure recovery handling willnot result in a race condition, meaning that the behaviour of thewireless communication network is dependent on timing of SCG failure,where the SCG configuration of the UE is different at the target SN andthe UE. It also ensures that the MN handles the SCG failure only ifnecessary, thereby preventing unnecessary signalling andreconfigurations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a LTE DC User Plane (UP) architecture;

FIG. 2 shows User Plane (UP) and Control Plane (CP) architectures forLTE-NR tight interworking;

FIG. 3 shows User Plane (UP) and Control Plane (CP) architectures forLTE-NR tight interworking;

FIG. 4 shows User Plane (UP) and Control Plane (CP) architectures forLTE-NR tight interworking;

FIG. 5a shows a schematic overview depicting a wireless communicationnetwork according to embodiments herein;

FIG. 5b shows a flowchart depicting a method according to embodimentsherein;

FIG. 5c shows a flowchart depicting a method according to embodimentsherein;

FIG. 5d shows a flowchart depicting a method according to embodimentsherein;

FIG. 6 shows a combined signalling scheme and flowchart according toembodiments herein;

FIG. 7 shows a combined signalling scheme according to embodimentsherein;

FIG. 8 shows a combined signalling scheme according to embodimentsherein;

FIG. 9 shows a combined signalling scheme according to embodimentsherein;

FIG. 10 shows a combined signalling scheme according to embodimentsherein;

FIG. 11 shows a combined signalling scheme according to embodimentsherein;

FIG. 12 shows a block diagram depicting a MN according to embodimentsherein;

FIG. 13 shows a block diagram depicting a UE according to embodimentsherein;

FIG. 14 shows a block diagram depicting a SN according to embodimentsherein;

FIG. 15 shows a telecommunication network connected via an intermediatenetwork to a host computer in accordance with some embodiments;

FIG. 16 shows a host computer communicating via a base station with auser equipment over a partially wireless connection in accordance withsome embodiments;

FIG. 17 shows methods implemented in a communication system including ahost computer, a base station and a user equipment in accordance withsome embodiments;

FIG. 18 shows methods implemented in a communication system including ahost computer, a base station and a user equipment in accordance withsome embodiments;

FIG. 19 shows methods implemented in a communication system including ahost computer, a base station and a user equipment in accordance withsome embodiments; and

FIG. 20 shows methods implemented in a communication system including ahost computer, a base station and a user equipment in accordance withsome embodiments.

DETAILED DESCRIPTION

Some of the embodiments contemplated herein will now be described morefully with reference to the accompanying drawings. Other embodiments,however, are contained within the scope of the subject matter disclosedherein, the disclosed subject matter should not be construed as limitedto only the embodiments set forth herein; rather, these embodiments areprovided by way of example to convey the scope of the subject matter tothose skilled in the art.

Embodiments herein relate to wireless communication networks in general.FIG. 5a is a schematic overview depicting a wireless communicationnetwork 1. The wireless communication network 1 comprises one or moreRadio Access Networks (RAN) and one or more Core Networks (CN). Thewireless communication network 1 may use one or a number of differenttechnologies. Embodiments herein relate to recent technology trends thatare of particular interest in a 5G context such as NR, however,embodiments are also applicable in further development of existingwireless communication systems such as e.g. Wideband Code DivisionMultiple Access (WCDMA) and LTE.

In the wireless communication network 1, wireless devices e.g. a UE 10such as a mobile station, a station (STA), a non-access point (non-AP)STA, a wireless device and/or a wireless terminal, communicate via oneor more Access Networks (AN), e.g. RAN, to one or more core networks(CN). It should be understood by the skilled in the art that “UE” is anon-limiting term which means any terminal, wireless communicationterminal, wireless device, Machine Type Communication (MTC) device,Device to Device (D2D) terminal, or node e.g. smart phone, laptop,mobile phone, sensor, relay, mobile tablets or any device capable ofcommunicating using radio communication with a radio network node withinan area served by the radio network node.

The wireless communication network 1 provides dual connectivity (DC)through a master node and a secondary node. Thus, the wirelesscommunication network 1 comprises a first radio network node, referredto as a master node (MN) 12, providing radio coverage over ageographical area, a first service area 11, of a first radio accesstechnology (RAT), such as NR, LTE, or similar. The master node 12 may bea transmission and reception point e.g. a radio network node such as aWireless Local Area Network (WLAN) access point or an Access PointStation (AP STA), an access node, an access controller, a base station,e.g. a radio base station such as a gNodeB (gNB), an evolved Node B(eNB, eNode B), a base transceiver station, a radio remote unit, anAccess Point Base Station, a base station router, a transmissionarrangement of a radio base station, a stand-alone access point or anyother network unit or node capable of communicating with a UE within thearea served by the master node 12 depending e.g. on the first radioaccess technology and terminology used. The MN 12 may be referred to asa master serving node wherein the first service area 11 may be referredto as a serving cell, and the MN 12 communicates with the UE 10 in formof DL transmissions to the UE 10 and UL transmissions from the UE 10.

The wireless communication network 1 further comprises a second radionetwork node, referred to as a secondary node (SN) 13, providing radiocoverage over a geographical area, a second service area 14, of a secondradio access technology (RAT), such as LTE, NR, or similar. The firstand second RATs may be different RATs. The secondary node 12 may be atransmission and reception point e.g. a radio network node such as aWLAN access point or an AP STA, an access node, an access controller, abase station, e.g. a radio base station such as a gNodeB (gNB), anevolved Node B (eNB, eNode B), a base transceiver station, a radioremote unit, an Access Point Base Station, a base station router, atransmission arrangement of a radio base station, a stand-alone accesspoint or any other network unit or node capable of communicating with aUE within the area served by the secondary node 13 depending e.g. on thesecond radio access technology and terminology used. The secondary nodemay be referred to as a secondary serving node wherein the secondservice area 14 may be referred to as a second serving cell, and the SN13 communicates with the UE 10 in form of DL transmissions to the UE 10and UL transmissions from the UE 10.

It should be noted that a service area may be denoted as cell, beam,beam group or similar to define an area of radio coverage.

The UE 10 is configured for communicating with the MN 12 and the SN 13with a first master configuration of e.g. bearers such as data and/orsignalling radio bearers, towards the MN 12 and obtains a firstsecondary configuration, a first SCG configuration, of e.g. bearers suchas signalling and/or data radio bearers, related to the secondary node13. Related to the secondary node 13 means that the radio interfaceconnection between the UE 10 and the secondary node 13 (or the radiointerface associated with the secondary node 13) is used to transferpackets associated with these bearers.

Embodiments herein may be related to the case when SCG SRB is notconfigured and all SN RRC messages are delivered embedded with the MCGSRB, or the case where SCG SRB is configured and the last SCGreconfiguration that was sent to the UE just before SCG failure was sentvia embedded RRC, e.g. due to a need for co-ordination with the MCG, orvia the SCG SRB.

Embodiments here are related to transmission of embedded RRC, i.e. alast SCG reconfiguration was (is) sent embedded within, or includedwith, an MN RRC message to the UE 10. It should further be noted:

-   -   Even though embodiments described herein focus on the LTE-NR        tight interworking case where the LTE is the master node        (referred to as EN-DC), embodiments are also applicable to other        DC cases such as NR-LTE DC where NR is the master and LTE is the        secondary node (referred to as NE-DC).    -   LTE and NR are the RATs that are covered in the description        herein. However, embodiments herein can be applicable to any        aggregation scenario where the MN and SN apply different        cellular/wireless RATs, such as Wi-FI, Zigbee, LoRA, Bluetooth,        etc.    -   X2 is referred to as the interface between the MN and SN, based        on the interface definitions in LTE. For LTE-NR interworking and        NR-NR interworking cases, the exact name for such an interface        could end up being different, e.g. Xn instead of X2, with the        corresponding XnAP protocol instead of X2AP. However, that will        not impact the applicability of embodiments.

The method actions performed by the UE 10 for handling communication,e.g. performing reconfiguration, in the wireless communication network 1providing DC communication according to embodiments herein will now bedescribed with reference to a flowchart depicted in FIG. 5b . Theactions do not have to be taken in the order stated below, but may betaken in any suitable order. Actions performed in some embodiments aremarked with dashed boxes. The dual connectivity is provided through themaster node 12 using a MCG over a first radio interface between the UE10 and the master node 12 and through the secondary node 13 using a SCGover a second radio interface between the UE 10 and the secondary node13. The first radio interface may be using a first radio accesstechnology, e.g. LTE, and the second radio interface may be using asecond radio access technology, e.g. NR. The first radio accesstechnology may thus be different from the second radio accesstechnology.

Action 501. The UE 10 detects a failure associated with the SCG,detecting e.g. a transmission error using the SCG, a radio link failurefor the SCG, a sync failure of the SCG, a SCG configuration failure,and/or an integrity check failure indication from SCG lower layers. TheUE 10 may detect the failure associated with the SCG upon detectingradio link failure for the SCG; upon detecting SCG change failure; orupon exceeding a maximum uplink transmission timing difference.

Action 502. The UE 10 suspends actions associated with the SCG. Forexample, the UE 10 may: suspend the SCG and SCG split data radiobearers; suspend the SCG SRB, if it was configured; suspend thetransmission/reception over the SCG radio, regardless of the destinationfor the message in the UL direction, i.e. even if it was intended forthe MN 12 as in the case of MCG split bearers; and/or suspend thetransmission of data or control signalling to the SN 13, e.g. if we havea split SCG bearer, do not use the functioning MN leg to send the datato the SN 13 via the MN 12.

Action 503. The UE 10 handles, e.g. performs, a reconfiguration of theSCG upon reception of an MCG RRC message with SCG configuration, byapplying the reconfiguration; and resuming or not resuming the suspendedactions associated with the SCG. An MCG RRC message means that it is anRRC message received on a MCG leg. Thus, the RRC message for the SCG maybe received embedded within an RRC message from the master node 12. Forexample, the UE 10 may perform the reconfiguration of the SCG byapplying the reconfiguration based on whether the UE 10 has started totransmit a RRC complete message or not. The UE 10 may perform thereconfiguration of the SCG in case the UE 10 has received an NR RRCmessage embedded within an MN RRC message, after the UE 10 has justdetected SCG failure and has suspended the SCG, by applying thereconfiguration

Additionally, the UE 10 may perform the reconfiguration of the SCG bysending an RRC complete message in an RRC message for the SCG directlyto the secondary node 13 or embedded within an RRC message to the masternode 12. E.g. the UE 10 may send an NR RRC complete message embeddedwithin an MN RRC message, upon the successful application of thereconfiguration. In some embodiments the UE 10 may, upon detecting anSCG failure, and the UE 10 has a pending RRC complete message to thelast SCG reconfiguration received via SCG SRB, perform thereconfiguration of the SCG by sending the RRC complete message via theMN 12, i.e. embedded via MN RRC message. The UE 10 may further, aftersending the complete message via the MN 12, send SCG failure informationto the MN 12. The UE 10 may, after sending the complete message via theMN 12, refrain from sending the SCG failure information to the MN 12,when the last SCG message that it has just applied was a mobilitymessage with the SN 13, and it has successfully managed to apply it andresume the SCG. The UE may thus discard the SCG failure informationbefore sending it to the MN 12.

Another example, the UE 10 may perform the reconfiguration of the SCG byresuming the suspended actions associated with the SCG. In someembodiments the UE 10 may perform the reconfiguration of the SCG byresuming any of: a SCG link; a SCG part of a split data radio bearer; aSCG signalling radio bearer, a transmission and/or reception over SCGradio, and/or a transmission of data or control signalling to thesecondary node (13). In some embodiments the UE 10 may perform thereconfiguration of the SCG by resuming the suspended SCG link or SCGestablishment if the received NR RRC message indicated mobility, or notresuming the suspended SCG link when the received NR RRC message notindicated mobility.

The method actions performed by the master node 12 for handlingcommunication in a wireless communication network 1, wherein the masternode 12 is configured to operate in cooperation with the secondary node13 to provide DC communication with the UE 10 through the master node 12using the MCG, over the first radio interface between the UE 10 and themaster node 12 and through the secondary node 13 using the SCG, over thesecond radio interface between the UE 10 and the secondary node 13,according to embodiments herein will now be described with reference toa flowchart depicted in FIG. 5c . The actions do not have to be taken inthe order stated below, but may be taken in any suitable order. Actionsperformed in some embodiments are marked with dashed boxes. The firstradio interface may be using a first radio access technology, e.g. LTE,and the second radio interface may be using a second radio accesstechnology, e.g. NR. The first radio access technology may thus bedifferent from the second radio access technology but may also be thesame RAT.

Action 511. The master node 12 receives from the UE 10, an indicationindicating a failure associated with the SCG.

Action 512. The master node 12 handles the failure based on whether oneor more conditions are fulfilled, and wherein handling the failurecomprises performing one or more of: postponing handling of the failure;performing a reconfiguration to the SCG; ignoring the failure; movingthe UE 10 to a different secondary node; providing the secondary node 13with a reconfiguration response message. The one or more conditions maycomprise whether the master node 12 has a pending reconfiguration forthe UE 10 for the SCG towards the secondary node 13. The one or moreconditions may comprise whether a mobility flag is set to true or falsein a reconfiguration message, from the secondary node 13. The one ormore conditions may comprise whether the master node 12 has started totransmit a reconfiguration message for the SCG before receiving theindication indicating the failure. The one or more conditions maycomprise whether the master node 12 has transmitted a reconfigurationmessage for the SCG and received or not received a reconfigurationresponse message before receiving the indication indicating the failure.The one or more conditions may comprise whether a last reconfigurationof the SCG was sent directly via the master node (12) or not.

Action 513. The master node 12 may transmit an RRC message for the SCGto the UE 10 embedded within an RRC message for the MCG.

The method actions performed by the secondary node 13 for handlingcommunication of the UE 10 in the wireless communication network 1,wherein the secondary node 13 is configured to operate in cooperationwith the master node to provide DC communication with the UE 10 throughthe secondary node 13 using the SCG over the second radio interfacebetween the UE 10 and the secondary node 13 and the master node 12 usingthe MCG over the first radio interface between the UE 10 and the masternode 12, according to embodiments herein will now be described withreference to a flowchart depicted in FIG. 5d . The actions do not haveto be taken in the order stated below, but may be taken in any suitableorder. Actions performed in some embodiments are marked with dashedboxes. The first radio interface may be using a first radio accesstechnology, e.g. LTE, and the second radio interface may be using asecond radio access technology, e.g. NR. The first radio accesstechnology may thus be different from the second radio access technologybut may also be the same RAT.

Action 521. The SN 13 transmits to the UE 10, an SCG reconfigurationmessage that includes a mobility flag wherein the mobility flag is setto true when the reconfiguration concerns mobility within the secondarynode and the mobility flag set to false or not included when thereconfiguration is not concerned with mobility within the secondarynode.

Action 522. The SN 13 may additionally or alternatively transmit to theUE 10 an SCG reconfiguration message.

Action 523. The SN 13 may additionally receive from the master node 12,a request to fetch the SCG configuration before an RRC complete messagecorresponding to the SCG reconfiguration has been received.

Action 524. The SN 13 may additionally transmit to the master node 12, aprevious SCG configuration message that the UE 10 was configured withbefore the SCG reconfiguration message was sent.

FIG. 6 is a combined signalling scheme and flowchart depicting someembodiments herein.

Action 601. The SN 13 transmits to the MN 12 an indication indicatingreconfiguration comprising a mobility flag set to true or false.

Action 602. The UE 10 detects SCG failure e.g. failure of the firstconfiguration for the secondary node and may transmit an indicationindicating SCG failure to the master node 12.

Action 603. The master node 12, upon getting the message, handles, e.g.performs, the SCG failure based upon whether one or more conditions arefulfilled. The one or more conditions may comprise: the MN has a pendingreconfiguration for the UE of a second secondary configuration ofbearers towards the secondary node; a mobility flag is set to TRUE in areconfiguration message from the SN 13; a mobility flag is set to FALSEin a reconfiguration message from the SN 13; has started to transmit areconfiguration message, e.g. a message 4, before receiving the SCGfailure and a last SCG reconfiguration was sent directly via SCG SRB.

The master node 12 may handle the SCG failure by performing one or moreof: postponing handling of the SCG failure; performing a reconfigurationto the second secondary configuration; ignoring the failure; moving theUE to a different SN; providing the SN with a reconfiguration responsemessage, e.g., when postponing the handling of the SCG failure.

In the flow in FIG. 7, the MN 12 receives the SCG failure (step 3) whenthe MN 12 has a pending SCG reconfiguration as indicated with the SCGReconfigure message received from the SN (step 2). The signallingbetween the MN and SN node could be over an X2 or Xn or similar networkinterface. In this case since the mobility flag is set to TRUE, the MNdecides to ignore the SCG failure, step 4, since it is likely that theSCG configuration received from the SN node will resolve the failure.For this reason, the MN 12 will continue with normal RRC reconfigurationprocedure (incl. SCG reconfiguration) step 5-8.

When the UE receives the SCG configuration which in this case containsmobility information for the SCG link, the UE will resume the SCG link.This also resets the SCG link monitoring. In case the resume of the SCGlink for some reason would fail the UE will trigger a new SCG failuretowards the MN node.

In the flow in FIG. 8, the MN 12 receives the SCG failure (step 3) whenit has a pending SCG reconfiguration as indicated with the SCGReconfigure message received from the SN 13 (step 2). In this case sincethe mobility flag is set to False or is absent the MN 12 decides tohandle the SCG failure, step 4. In this case it also notifies the old SNnode 13 in step 5 about the failure to deliver the SCG configuration tothe UE 10. This will mean that the SN 13 will revert to the old SCGconfiguration which is currently used in the UE 10.

The rest of the flow shows the case the MN 12 decides to handle the SCGfailure by moving the UE 10 to a different SN 15. Also, other cases canbe considered were the MN 12 decides to keep the UE 10 in the same SN 13(possible in a different cell). The following optional steps can beperformed:

-   -   Step 6 the MN 12 fetches the latest valid UE configuration (this        step could actually be combined with step 5)    -   Step 7 the MN 12 performs an SN addition in the new SN 15. The        SN addition may contain the last valid UE configuration enabling        the target node to perform delta signalling towards the UE 10        (delta signalling is more efficient to “full configuration”        since the parameters of the UE configuration that does not need        to be changed does not need to be signaled).    -   Step 8 the new SN node 15 generates an SCG configuration which        will be sent to the UE 10 via the MN 12 (in the SN addition        acknowledge).    -   Step 9-12 is a normal UE configuration and SN addition with the        difference that when UE 10 receives message 9 the UE 10 will (in        step 10) resume the SCG link since the SCG configuration        contains SCG mobility information. This also resets the SCG link        monitoring. In case the resume of the SCG link for some reason        would fail the UE10 will trigger a new SCG failure towards the        MN 12.

The flow in FIG. 9 shows another variant of the case the mobility flagis set to

False or absent. In this case the MN 12 continues with the SCGreconfiguration as normal (Step 4-6) before the MN 12 handles the SCGfailure. This may be useful in the case the MN 12 has started totransmit message 4 before receiving the SCG failure (Step 3). In thiscase the UE 10 will accept the new SCG reconfiguration but the UE 10will not resume SCG link, e.g. because the SCG configuration may notcontain SCG mobility information. Step 6 could be a new message to letthe SN 13 know that the SCG reconfiguration that the SN 13 has last senthas succeeded, or it could be a simple forwarding of the RRC completemessage embedded within message 5.

The rest of the flow shows the case the MN 12 decides to handle the SCGfailure by moving the UE 10 to the different SN 15. Also, other casescan be considered were the MN 12 decides to keep the UE 10 in the sameSN 13 (possible in a different cell). The following optional steps canbe performed:

-   -   Step 8 the MN 12 fetches the latest valid UE configuration for        the UE 10 from the SN 13.    -   Step 9 the MN 12 performs an SN addition to the different SN 15.        The SN addition may contain the last valid UE configuration        enabling the target node, i.e. the different SN 15, to perform        delta signalling towards the UE 10 (delta signalling is more        efficient to “full configuration” since the parameters of the UE        configuration that does not need to be changed does not need to        be signaled).    -   Step 10 the different SN 15 generates an SCG configuration which        will be sent to the

UE 10 via the MN 12 (in the SN addition acknowledge).

-   -   Step 11-14 is a normal UE configuration and SN addition with the        difference that when UE 10 receives message 11 the UE 10 will        (in step 11) resume the SCG link since the SCG configuration        contain SCG mobility information. This also restarts the SCG        link monitoring. In case the resume of the SCG link for some        reason would fail the UE 10 will trigger a new SCG failure        towards the MN 12.

The flow in FIG. 10 shows another embodiment where the MN 12 does notreceive any information about the SCG configuration from the SN 13. Inthis case the MN 12 continues with the SCG reconfiguration as normal(Step 4-6) before the MN 12 handles the SCG failure. In this embodiment,the UE 10 accepts the new SCG configuration but it does not resume theSCG link until it receives an explicit indication from the MN 12 (step11).

After step 4-6 the rest of the flow shows the case the MN 12 decides tohandle the SCG failure by moving the UE 10 to the different SN 15. Also,other cases can be considered were the MN 12 decides to keep the UE 10in the same SN 13 (possible in a different cell). The following optionalsteps can be performed:

-   -   Step 8 the MN 12 fetches the latest valid UE configuration    -   Step 9 the MN 12 performs an SN addition to the different SN 15.        The SN addition may contain the last valid UE configuration        enabling the different SN 15 to perform delta signalling towards        the UE 10 (delta signalling is more efficient to “full        configuration” since the parameters of the UE configuration that        does not need to be changed does not need to be signaled).    -   Step 10 the different SN 15 generates an SCG configuration which        will be sent to the UE 10 via the MN 12 (in the SN addition        acknowledge).    -   Step 11-14 is a normal UE configuration and SN addition with the        difference that when UE 10 receives message 11 the UE 10 may (in        step 12) resume the SCG link since MN 12 included a specific        indication (e.g. Resume Flag or other) in message 11. This also        restarts the SCG link monitoring. In case the resume of the SCG        link for some reason would fail the UE 10 will trigger a new SCG        failure towards the MN 12.

The flow in FIG. 11 shows another embodiment where the MN 12 does notreceive any information about the SCG configuration from the SN 13. Inthis case the MN 12 continues with the SCG reconfiguration as normal(Step 4-6) before the MN 12 handles the SCG failure. In this embodiment,the UE 10 accepts the new SCG configuration but it does not resume theSCG link until the UE 10 receives an explicit indication from the MN 12(step 11).

After step 4-6 the rest of the flow shows the case the MN 12 decides tohandle the SCG failure by moving the UE 10 to the different SN 15. Also,other cases can be considered were the MN 12 decides to keep the UE 10in the same SN 13 (possible in a different cell). The following optionalsteps can be performed:

-   -   Step 8 the MN 12 fetches the latest valid UE configuration    -   Step 9 the MN 12 performs an SN addition to the different SN 15.        The SN addition may contain the last valid UE configuration        enabling the different SN 15 to perform delta signalling towards        the UE 10 (delta signalling is more efficient to “full        configuration” since the parameters of the UE configuration that        does not need to be changed does not need to be signaled).    -   Step 10 the different SN 15 generates an SCG configuration which        will be sent to the UE 10 via the MN 12 (in the SN addition        acknowledge).    -   Step 11-14 is a normal UE configuration and SN addition with the        difference that when UE 10 receives message 11 the UE 10 will        (in step 12) resume the SCG link since MN 12 included a specific        indication (e.g. Resume Flag or other) in message 11. This also        restarts the SCG link monitoring. In case the resume of the SCG        link for some reason would fail the UE 10 will trigger a new SCG        failure towards the MN 12.

Below are some examples of embodiments disclosed for handling a SCGfailure in the wireless communication network 1.

Option 1: a first flag is introduced in an X2 message to indicate if NRmessage is concerning mobility.

Embodiment 1: The SN 13, upon sending an SCG reconfiguration to the UE10 that is concerned with mobility within the SN 13 (e.g., SCelladdition, PScell change, etc.), includes a flag indicating so.

Embodiment 2: The indication flag according to embodiment 1 may be anoptional IE in the X2 RRC Transfer message, a value of TRUE indicatingthe embedded message is related to mobility and a value of FALSE or thelack of inclusion of the IE indicating the message is not related tomobility.

Embodiment 3: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and discovering that an NR RRC message is pendingto be transmitted to the UE 10 embedded within an MN RRC message, andthat the SN 13 has indicated a mobility flag according to embodiment 1,will ignore the SCG failure information report, and instead forward thepending NR RRC message to the UE 10.

Embodiment 4: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and the MN 12 has initiated transmission to the UE10 or just successfully sent to the UE 10 an NR RRC message embeddedwithin an MN RRC message, and that the SN 13 has indicated a mobilityflag according to embodiment 1 when transferring this message to the MN12, and it has not yet received an RRC complete message regarding thismessage, will ignore the SCG failure information report.

Embodiment 5: An embodiment according to embodiments 3 or 4, where theMN 12, upon receiving an RRC complete message to the last NR RRC messagesent embedded within an MN RRC message, forwards the complete message tothe SN 13.

Embodiment 6: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and discovering that an NR RRC message is pendingto be transmitted to the UE 10 embedded within an MN RRC message, andthat the SN 13 has not indicated a mobility flag according to embodiment1, postpones the handling of the SCG failure information report andinstead forwards the pending NR RRC message embedded within an MN RRCmessage.

Embodiment 7: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and the MN 12 has initiated transmission to the UE10 or just successfully sent to the UE 10 an NR RRC message embeddedwithin an MN RRC message, and that the SN 13 has not indicated amobility flag according to embodiment 1 when transferring this messageto the MN 12, and the MN 12 has not yet received an RRC complete messageregarding this message, postpones the handling of the SCG failureinformation report.

Embodiment 8: An embodiment according to embodiments 6 or 7, where theMN 12, upon receiving an RRC complete message to the last NR RRC messagesent embedded within an MN RRC message, forwards the complete message tothe SN 13.

Embodiment 9: An embodiment according to embodiment 8, where the MN 12decides to change to a second SN, and requests the current SN 13 thelatest SCG configurations, releases the SN 13 and adds another SN,indicating the latest SCG reconfiguration received from the SN 13 thatit just released, so that the new SN can apply delta configuration.

Embodiment 10: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and discovering that an NR RRC message is pendingto be transmitted to the UE 10 embedded within an MN RRC message, andthat the SN 13 has not indicated a mobility flag according to embodiment1, discards the pending RRC message, request the current SN 13 thelatest SCG configuration with a “previous” flag indicating to the SN 13to send it the latest configuration acknowledged by the UE 10, releasesthe SN 13 and adds another SN, indicating the SCG configuration receivedfrom the SN 13 that it just released, so that the new SN can apply thedelta configuration.

Embodiment 11: An embodiment according to embodiment 9 or 10, where theMN 12 forwards the SCG reconfiguration message to the UE 10 embeddedwithin an MN RRC message.

Option 2: no flag is introduced in an X2 message to indicate if NRmessage is concerning mobility, instead is an explicit resume indicationintroduced and transmitted from the MN 12

Embodiment 12: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and discovering that an NR RRC message is pendingto be transmitted to the UE 10 embedded within an MN RRC message,postpones the handling of the SCG failure information report and insteadforwards the pending NR RRC message embedded within an MN RRC message.

Embodiment 13: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and the MN 12 has initiated transmission to the UE10 or just successfully sent to the UE 10 an NR RRC message embeddedwithin an MN RRC message, and the MN 12 has not yet received an RRCcomplete message regarding this message, postpones the handling of theSCG failure information report.

Embodiment 14: An embodiment according to embodiments 12 or 13, wherethe MN 12, upon receiving an RRC complete message to the last NR RRCmessage sent embedded within an MN RRC message, forwards the completemessage to the SN 13.

Embodiment 15: An embodiment according to embodiment 14, where the MN 12decides to change the SN 13, and requests the current SN 13 the latestSCG configurations, releases the SN 13 and adds another SN, indicatingthe latest SCG reconfiguration received from the SN 13 that it justreleased, so that the new SN can apply delta configuration.

Embodiment 16: The MN 12, upon receiving an SCG failure informationreport from the UE 10 and discovering that an NR RRC message is pendingto be transmitted to the UE 10 embedded within an MN RRC message,discards the pending RRC message, request the current SN 13 the latestSCG configuration with a “previous” flag indicating to the SN 13 to sendit the latest configuration acknowledged by the UE 10, releases the SN13 and adds another SN, indicating the SCG configuration received fromthe SN 13 that it just released, so that the new SN can apply the deltaconfiguration.

Embodiment 17: An embodiment according to embodiment 15 or 16, where theMN 12 forwards the SCG reconfiguration message to the UE 10 embeddedwithin an MN RRC message, and includes a resume flag in the MN part ofthe message to indicate to the UE 10 that it can resume the suspendedSCG.

Embodiment 18: The MN 12, upon receiving an SCG failure informationreport from the UE 10, discards any pending NR RRC messages, releasesthe SN 13, putting the UE 10 out of dual connectivity. This may beperformed both in option 1 and for option 2 above.

UE embodiments:

Applicable to both options mentioned above

Embodiment 19: The UE 10, where upon reception of an NR RRC messageembedded within an MN RRC message, after it has just detected SCGfailure and has suspended the SCG, will apply the reconfiguration.

Embodiment 20: The UE 10 sends the NR RRC complete message embeddedwithin an MN RRC message, upon the successful application of theconfiguration.

Applicable to option 1 wherein the first flag is introduced in X2 toindicate if NR message is concerning mobility:

Embodiment 21: An embodiment according to embodiment 19, whereby if thereceived NR RRC message indicated mobility, the UE 10 will resume thesuspended SCG link or SCG establishment.

Embodiment 22: An embodiment according to embodiment 19, whereby if thereceived NR RRC message not indicated mobility, the UE 10 will notresume the suspended SCG link.

Applicable to option 2 wherein no flag is introduced in X2 message toindicate if NR message is concerning mobility:

Embodiment 23: An embodiment according to embodiment 19, whereby the UE10 resumes the suspended SCG link only if the MN RRC message indicatesan explicit resume flag.

Embodiment 24: An embodiment according to embodiment 19, whereby if thereceived NR RRC message not including an explicit resume flag, the UE 10will not resume the suspended SCG link.

Applicable to both options above.

Embodiment 25: An embodiment according to embodiment 21 or 23, wherebythe UE 10 indicates to the MN or the SN in the LTE or NR RRC completemessage that it has resumed the suspended SCG link.

Embodiments related to SCG SRB, i.e. last SCG reconfiguration was(being) sent directly via SCG SRB.

UE part:

Embodiment 26: The UE 10 upon detecting an SCG failure, and it has apending RRC complete message to the last SCG reconfiguration receivedvia SCG SRB, will send the RRC complete message via the MN 12 (i.e.embedded via MN RRC message).

Embodiment 27: The UE 10, after sending the complete message via the MNaccording to embodiment 26, sends the SCG failure information to the MN12.

Embodiment 28: The UE 10, after sending the complete message via the MN,refrains sending the SCG failure information to the MN 12 according toembodiment 26, if the last SCG message that it has just applied was amobility message with the SN 13, and it has successfully managed toapply it and resume the SCG, will discard the SCG failure informationbefore sending it to the MN 12.

Network part:

Embodiment 29: The SN 13, upon getting a request to fetch an SCGconfiguration from the SN 13, if it has been waiting for a completemessage to the last SCG reconfiguration that the SN 13 has sent via SCGSRB, will respond to the MN 12 with the previous SCG configuration (i.e.the last SCG reconfiguration that the SN 13 has received a completemessage to).

Embodiment 30: The SN 13, upon getting a request to fetch an SCGconfiguration from the SN 13, if the SN 13 has been waiting for acomplete message to the last SCG reconfiguration that the SN 13 has sentvia SCG SRB, will respond to the MN 12 with an empty message (e.g. anempty SCG configuration) optionally indicating that it does not have avalid configuration.

Embodiment 31: The MN 12, upon getting an empty SCG configurationaccording to embodiment 30, considers delta configuration is notapplicable, and thus will not include SCG configuration in the SNaddition request message that it sends to a target SN, if it decides tochange the SN (i.e. only full configuration is applicable).

FIG. 12 is a block diagram depicting a first radio network node such asthe master node 12 for handling communication in a wirelesscommunication network, wherein the master node 12 is configured tooperate in cooperation with a secondary node to provide DC communicationwith the UE 10 through the master node 12 using the MCG over the firstradio interface between the UE 10 and the master node 12 and through thesecondary node 13 using the SCG over the second radio interface betweenthe UE 10 and the secondary node 13. The first radio interface may beusing a first radio access technology and the second radio interface maybe using a second radio access technology, and wherein the first radioaccess technology is different from the second radio access technology.

The master node and the secondary node are configured for communicatingwith the UE 10. The master node may be configured with the first masterconfiguration of bearers, e.g. signalling and/or data radio bearers,towards the UE 10 and the UE 10 has obtained the first secondaryconfiguration of bearers, e.g. signalling or data radio bearers, relatedto the secondary node 13. I.e. the MN 12 may be configured with a MCGlink to the UE 10 and the UE 10 may be configured for a SCG link to theSN 13 e.g. UE has been configured with a secondary radio interfaceconfiguration associated with the secondary node. The master node 12 maycomprise processing circuitry 1201, e.g. one or more processors,configured to perform the methods herein. The MN 12 and/or theprocessing circuitry 1201 may be configured to transmit the RRC messagefor the SCG to the UE 10 embedded within an RRC message for the MCG.

The master node 12 may comprise a receiving circuit 1202, e.g. areceiver or a transceiver. The master node 12, the processing circuitry1201, and/or the receiving circuit 1202 is configured to receive fromthe UE 10, the indication indicating the failure associated with the SCGe.g. receive an indication indicating failure of the first secondaryconfiguration.

The master node 12 may comprise a handling circuit 1203. The master node12, the processing circuitry 1201, and/or the handling circuit 1203 isconfigured to handle the failure based on whether one or more conditionsare fulfilled, and wherein handle the failure comprises performing oneor more of: postponing handling of the failure; performing areconfiguration to the SCG; ignoring the failure; moving the UE 10 to adifferent secondary node; providing the secondary node 13 with the areconfiguration response message. The one or more conditions maycomprise whether the master node 12 has a pending reconfiguration forthe UE 10 for the SCG towards the secondary node. The one or moreconditions may comprise whether a mobility flag is set to true or falsein a reconfiguration message, from the secondary node 13. The one ormore conditions may comprise whether the master node 12 has started totransmit a reconfiguration message for the SCG before receiving theindication indicating the failure. The one or more conditions maycomprise whether the master node 12 has transmitted a reconfigurationmessage for the SCG and received or not received a reconfigurationresponse message before receiving the indication indicating the failure.The one or more conditions may comprise whether a last reconfigurationof the SCG was sent directly via the master node 12 or not.

E.g. to handle the SCG failure based on whether one or more conditionsare fulfilled wherein the one or more conditions may comprise: the MN 12has a pending SCG reconfiguration; a mobility flag is set to TRUE in areconfiguration message from the SN 13; a mobility flag is set to FALSEin a reconfiguration message from the SN 13; has started to transmit areconfiguration message before receiving the SCG failure, and a last SCGreconfiguration was sent directly via SCG SRB. The master node mayhandle the SCG failure by performing one or more of: postponing handlingof the SCG failure; performing a reconfiguration to the second secondaryconfiguration; ignoring the failure; moving the UE to a different SN;providing the SN with a reconfiguration response message, e.g. whenpostponing the handling of the SCG failure.

The MN 12 further comprises a memory 1205. The memory comprises one ormore units to be used to store data on, such as signal strengths orqualities, ID of UEs, IDs of radio network nodes, MSG configurations;SCG configurations, flags, applications to perform the methods disclosedherein when being executed, and similar.

The methods according to the embodiments described herein for the MN 12are respectively implemented by means of e.g. a computer program 1206 ora computer program product, comprising instructions, i.e., software codeportions, which, when executed on at least one processor, cause the atleast one processor to carry out the actions described herein, asperformed by the MN 12. The computer program 1206 may be stored on acomputer-readable storage medium 1207, e.g. a disc, a USB stick orsimilar. The computer-readable storage medium 1207, having stored thereon the computer program, may comprise the instructions which, whenexecuted on at least one processor, cause the at least one processor tocarry out the actions described herein, as performed by the MN 12. Insome embodiments, the computer-readable storage medium may be atransitory or a non-transitory computer-readable storage medium.

FIG. 13 is a block diagram depicting the user equipment 10 for handlingcommunication in a wireless communication network providing DCcommunication through the MN 12 using the MCG over the first radiointerface between the UE and the MN 12 and through the SN 13 using theSCG over the second radio interface between the UE 10 and the secondarynode 13. The UE may be configured for communicating with a master nodeand a secondary node with a first master configuration of bearerstowards the master node and a first secondary configuration of bearerstowards the secondary node. The UE 10 may receive, at least partly, areconfiguration indication indicating a second secondary configurationof bearers, i.e. SCG link, towards the secondary node. The first radiointerface may be using a first radio access technology and the secondradio interface may be using a second radio access technology, whereinthe first radio access technology is different from the second radioaccess technology.

The UE 10 may comprise processing circuitry 1301, e.g. one or moreprocessors, configured to perform the methods herein.

The UE 10 may comprise a detecting circuit 1302, e.g. a transmitter or atransceiver. The UE 10, the processing circuitry 1301, and/or thedetecting circuit 1302 is configured to detect the failure associatedwith the SCG such as a SCG failure.

The UE 10 may comprise a transmitting circuit 1304, e.g. a transmitteror a transceiver. The UE 10, the processing circuitry 1301, and/or thetransmitting circuit 1304 may be configured to transmit the indicationindicating failure of the first secondary configuration.

The UE 10 may comprise a handling circuit 1303. The UE, the processingcircuitry 1301, and/or the handling circuit 1304 is configured tosuspend actions associated with the SCG, e.g. suspend SCG link; SCGsplit data radio bearer; SCG signalling radio bearer, transmissionand/or reception over SCG radio, and/or transmission of data or controlsignalling to the secondary node 13. The UE, the processing circuitry1301, and/or the handling circuit 1303 is configured to handle, e.g.perform, the reconfiguration of the SCG upon reception of the MCG RRCmessage comprising SCG configuration, by being configured to apply thereconfiguration; and resume or not resume the suspended actionsassociated with the SCG. The MCG RRC message for the SCG may be receivedembedded within the RRC message from the MN 12. The UE, the processingcircuitry 1301, and/or the handling circuit 1303 may be configured toperform the failure of the first secondary configuration, denoted SCGfailure, based on whether one or more conditions are fulfilled.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to perform the reconfiguration of SCG by applying thereconfiguration based on whether the UE 10 has started to transmit a RRCcomplete message or not.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to perform the reconfiguration of the SCG by beingconfigured to send an RRC complete message in an RRC message for the SCGdirectly to the secondary node 13 or embedded within an RRC message tothe master node 12.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to perform the reconfiguration of SCG by beingconfigured to resume the suspended actions associated with the SCG byresuming any of: the SCG link; the SCG part of the split data radiobearer; the SCG signalling radio bearer; the transmission and/orreception over SCG radio, and/or the transmission of data or controlsignalling to the secondary node (13).

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to, upon reception of an RRC message embedded withinan MN RRC message, after it has just detected SCG failure and hassuspended the SCG link, apply the reconfiguration.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to send the RRC complete message embedded within an MNRRC message, upon the successful application of the configuration.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to, whereby if the received RRC message indicatedmobility, resume the suspended SCG link.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to, whereby if the received RRC message not indicatedmobility, not resume the suspended SCG link.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to, whereby if the received RRC message not includingan explicit resume flag, not resume the suspended SCG link.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured indicate to the MN 12 or the SN 13 in an RRC completemessage that it has resumed the suspended SCG link.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to, upon detecting an SCG failure, and it has apending RRC complete message to the last SCG reconfiguration receivedvia SCG SRB, send the RRC complete message via the MN 12 (i.e. embeddedvia MN RRC message). This may be the case when a last reconfiguration isreceived directly from the secondary node 13.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to, after sending the complete message via the MN,send the SCG failure information to the MN 12. This may be the case whena last reconfiguration is received directly from the secondary node 13.

The UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to, after sending the complete message via the MN,refrain sending the SCG failure information to the MN 12, if a last SCGmessage that it has just applied was a mobility message with the SN 13,and the UE 10 has successfully managed to apply it and resume the SCG,the UE, the processing circuitry 1301, and/or the handling circuit 1303may be configured to discard the SCG failure information before sendingit to the MN 12. This may be the case when a last reconfiguration isreceived directly from the secondary node 13.

The one or more conditions may comprise: reception of an RRC messageembedded within an MN RRC message from the MN 12; the received RRCmessage indicates mobility or not; the UE 10 has a pending SCGreconfiguration; the received RRC message not including an explicitresume flag or includes an explicit resume flag; and/or has started totransmit RRC complete or not.

The handling may comprise: postponing transmission of indication offailure, refraining transmission of the indication of failure; sendingcomplete message to the MN 12; applying reconfiguration; and/or resumeor not resume suspended SCG link.

The UE 10 further comprises a memory 1305. The memory comprises one ormore units to be used to store data on, such as signal strengths orqualities, IDs of radio network nodes, MSG configurations; SCGconfigurations, flags, applications to perform the methods disclosedherein when being executed, and similar.

The methods according to the embodiments described herein for the UE 10are respectively implemented by means of e.g. a computer program 1306 ora computer program product, comprising instructions, i.e., software codeportions, which, when executed on at least one processor, cause the atleast one processor to carry out the actions described herein, asperformed by the UE 10. The computer program 1306 may be stored on acomputer-readable storage medium 1307, e.g. a disc, a USB stick orsimilar. The computer-readable storage medium 1307, having stored thereon the computer program, may comprise the instructions which, whenexecuted on at least one processor, cause the at least one processor tocarry out the actions described herein, as performed by the UE 10. Insome embodiments, the computer-readable storage medium may be atransitory or a non-transitory computer-readable storage medium.

FIG. 14 is a block diagram depicting a second radio network node such asthe secondary node 13 for handling communication the UE in the wirelesscommunication network 1. The secondary node is configured to operate incooperation with a master node to provide DC communication with the UE10 through the secondary node 13 using the SCG over the second radiointerface between the UE 10 and the secondary node 13 and the masternode 12 using the MCG over the first radio interface between the UE 10and the master node 12. E.g. the master node and the secondary node areconfigured for communicating with the UE 10. The master node 12 may beconfigured with the UE 10 with a first master configuration of bearers,i.e. a first MCG link, towards the master node and the UE 10 may furtherbe configured with a first secondary configuration of bearers, i.e.first SCG link, towards the secondary node 13.

The SN 13 may comprise processing circuitry 1401, e.g. one or moreprocessors, configured to perform the methods herein.

The SN 13 may comprise a transmitting circuit 1402, e.g. a transmitteror a transceiver. The SN 13, the processing circuitry 1401, and/or thetransmitting circuit 1402 is configured to transmit to the userequipment, an SCG reconfiguration message that includes a mobility flagwherein the mobility flag is set to true when the reconfigurationconcerns mobility within the secondary node and the mobility flag set tofalse or not included when the reconfiguration is not concerned withmobility within the secondary node. E.g. to transmit, upon sending areconfiguration of the SCG to the UE 10 that is concerned with mobilitywithin the SN 13 (e.g. SCell addition, PScell change, etc.), includesthe flag indicating so to the MN 12. The indication flag may be anoptional IE in the X2 RRC Transfer message, a value of TRUE indicatingthe embedded message is related to mobility and a value of FALSE or thelack of inclusion of the IE indicating the message is not related tomobility. The SN 13, the processing circuitry 1401, and/or thetransmitting circuit 1402 may be configured to transmit to the userequipment 10 the SCG reconfiguration message.

The SN 13 may comprise a handling circuit 1403. The SN 13, theprocessing circuitry 1401, and/or the handling circuit 1403 may beconfigured to handle the SCG failure based on whether one or moreconditions are fulfilled. The one or more conditions may comprise: upongetting a request to fetch an SCG configuration from the SN 13, if ithas been waiting for a complete message to the last SCG reconfigurationthat the SN 13 has sent via SCG SRB. The SN 13 may handle the SCGfailure by e.g. respond to the MN 12 with a previous SCG configuration;and/or with an empty message.

The SN 13, the processing circuitry 1401, and/or the handling circuit1403 may be configured to, upon getting a request to fetch an SCGconfiguration from the SN 13, if it has been waiting for a completemessage to the last SCG reconfiguration that the SN 13 has sent via SCGSRB, respond to the MN 12 with a previous SCG configuration (i.e. thelast SCG reconfiguration that the SN 13 has received a complete messageto).

The SN 13, the processing circuitry 1401, and/or the handling circuit1403 may be configured to, upon getting a request to fetch an SCGconfiguration from the SN 13, if the SN 13 has been waiting for acomplete message to the last SCG reconfiguration that the SN 13 has sentvia SCG SRB, respond to the MN 12 with an empty message (e.g. an emptySCG configuration) optionally indicating that it does not have a validconfiguration.

The SN 13, the processing circuitry 1401, and/or the handling circuit1403 may be configured to receive, from the master node 12, a request tofetch the SCG configuration before an RRC complete message correspondingto the SCG reconfiguration has been received. The SN 13, the processingcircuitry 1401, and/or the handling circuit 1403 may be configured totransmit to the master node 12, a previous SCG configuration messagethat the UE was configured with before the SCG reconfiguration messagewas sent.

The SN 13 further comprises a memory 1405. The memory comprises one ormore units to be used to store data on, such as signal strengths orqualities, IDs of radio network nodes, SCG configurations, flags,applications to perform the methods disclosed herein when beingexecuted, and similar.

The methods according to the embodiments described herein for the SN 13are respectively implemented by means of e.g. a computer program 1406 ora computer program product, comprising instructions, i.e., software codeportions, which, when executed on at least one processor, cause the atleast one processor to carry out the actions described herein, asperformed by the SN 13. The computer program 1406 may be stored on acomputer-readable storage medium 1407, e.g. a disc, a USB stick orsimilar. The computer-readable storage medium 1407, having stored thereon the computer program, may comprise the instructions which, whenexecuted on at least one processor, cause the at least one processor tocarry out the actions described herein, as performed by the SN 13. Insome embodiments, the computer-readable storage medium may be atransitory or a non-transitory computer-readable storage medium.

In some embodiments, the computer-readable storage medium may be atransitory or a non-transitory computer-readable storage medium,volatile or non-volatile computer readable memory including, withoutlimitation, persistent storage, solid-state memory, remotely mountedmemory, magnetic media, optical media, random access memory (RAM),read-only memory (ROM), mass storage media (for example, a hard disk),removable storage media (for example, a flash drive, a Compact Disk (CD)or a Digital Video Disk (DVD)), and/or any other volatile ornon-volatile, non-transitory device readable and/or computer-executablememory devices that store information, data, and/or instructions thatmay be used by processing circuitry. Device readable medium may storeany suitable instructions, data or information, including a computerprogram, software, an application including one or more of logic, rules,code, tables, etc. and/or other instructions capable of being executedby processing circuitry and, utilized by the MN 12.

Processing circuitry may comprise a combination of one or more of amicroprocessor, controller, microcontroller, central processing unit,digital signal processor, application-specific integrated circuit, fieldprogrammable gate array, or any other suitable computing device,resource, or combination of hardware, software, and/or encoded logicoperable to provide, either alone or in conjunction with other UEcomponents, such as device readable medium functionality. Suchfunctionality may include providing any of the various wireless featuresor benefits discussed herein. For example, processing circuitry mayexecute instructions stored in device readable medium or in memorywithin processing circuitry to provide the functionality disclosedherein.

According to an aspect the embodiments herein provide a method performedby a master node for handling communication in a wireless communicationnetwork. The master node and a secondary node, in the wirelesscommunication network, are configured for communicating with the UE. Themaster node is configured with a first master configuration of bearers,e.g. signalling and/or data radio bearers, towards the UE and the UE hasobtained a first secondary configuration of bearers, e.g. signalling ordata radio bearers, related to the secondary node e.g. the UE hasreceived a first secondary configuration of bearers towards thesecondary node. I.e. the MN is configured with a MCG link to the UE andthe UE configured for a SCG link to the SN e.g. UE has been configuredwith a secondary radio interface configuration associated with thesecondary node. The master node receives an indication indicatingfailure of the first secondary configuration, e.g. radio conditions arenot good enough to maintain communication over a radio interface to thesecondary node. The MN handles the SCG failure or a reconfiguration ofthe configuration of bearers, i.e. reconfiguration of the SCG link,towards the secondary node based on whether one or more conditions arefulfilled. The one or more conditions may comprise: the MN has a pendingreconfiguration for the UE of a second secondary configuration ofbearers, i.e. the SCG link, towards the secondary node; a mobility flagis set to TRUE in a reconfiguration message from the SN; a mobility flagis set to FALSE in a reconfiguration message from the SN; has started totransmit a reconfiguration message before receiving the SCG failure; hastransmitted a reconfiguration message but not yet received anreconfiguration response message before receiving the SCG failure; hastransmitted a reconfiguration message and have received anreconfiguration response message before receiving the SCG failure, and alast SCG reconfiguration was sent directly via MN or not. The masternode may handle the SCG failure by performing one or more of: postponinghandling of the SCG failure; performing a reconfiguration to the secondsecondary configuration; ignoring the failure; moving the UE to adifferent SN; providing the SN with the an reconfiguration responsemessage, e.g. when postponing the handling of the SCG failure.

According to another aspect embodiments herein provide a methodperformed by a UE for handling communication in a wireless communicationnetwork. The UE is configured for communicating with a master node and asecondary node with a first master configuration of bearers towards themaster node and a first secondary configuration of bearers towards thesecondary node. The UE detects failure of the first secondaryconfiguration. The UE handles a reconfiguration of bearers, or SCG link,towards the secondary node, e.g. to a second or the first secondaryconfiguration, based on whether one or more conditions are fulfilled.The one or more conditions may comprise: reception of an RRC messageembedded within an MN RRC message from the MN or SN; the received RRCmessage indicates mobility or not; the UE 10 has a pending SCGreconfiguration; the received RRC message not including an explicitresume flag or includes an explicit resume flag; and/or has started totransmit RRC complete or not. The manner of handling the reconfigurationmay comprise: postponing transmission of indication of failure,refraining transmission of the indication of failure; sending completemessage to the MN; applying reconfiguration; and/or resuming or notresuming suspended SCG link, i.e. radio configuration of the secondaryradio interface.

According to yet another aspect of embodiments herein a method performedby a secondary node for handling communication of a wireless device in awireless network is herein provided. The secondary node and a masternode, in the wireless communication network, are configured forcommunicating with the UE. The secondary node is configured with a firstsecondary configuration of bearers, i.e. a SCG link, towards the UE andthe UE is further configured with a master configuration of bearerstowards the master node. The secondary node transmits a mobility flagset to true or false in a reconfiguration message to the MN. Thesecondary node may further handle a reconfiguration procedure of bearersto the UE, e.g. to a second or the first secondary configuration, basedon whether one or more conditions are fulfilled. The conditions maycomprise: a last SCG reconfiguration was sent directly via SCG SRB; upongetting a request to fetch an SCG configuration and been waiting for acomplete message to the last SCG reconfiguration that the SN has sentvia SCG SRB. The conditions may also comprise: a last SCGreconfiguration was sent via MN node; upon getting a request to fetch anSCG configuration and been waiting for a complete message to the lastSCG reconfiguration was sent via MN node. The SN may handle thereconfigurations procedure by: responding to the MN with a previous SCGconfiguration; or respond to the MN with an empty optionally indicatingthat it does not have a valid configuration.

Also, a master node, a UE and a secondary node are provided hereinconfigured to perform the methods disclosed herein.

FIG. 15: Telecommunication network connected via an intermediate networkto a host computer in accordance with some embodiments

With reference to FIG. 15, in accordance with an embodiment, acommunication system includes telecommunication network QQ410, such as a3GPP-type cellular network, which comprises access network QQ411, suchas a radio access network, and core network QQ414. Access network QQ411comprises a plurality of base stations QQ412 a, QQ412 b, QQ412 c, suchas NBs, eNBs, gNBs or other types of wireless access points beingexamples of the master and secondary nodes above, each defining acorresponding coverage area QQ413 a, QQ413 b, QQ413 c. Each base stationQQ412 a, QQ412 b, QQ412 c is connectable to core network QQ414 over awired or wireless connection QQ415. A first UE QQ491 located in coveragearea QQ413 c is configured to wirelessly connect to, or be paged by, thecorresponding base station QQ412 c. A second UE QQ492 in coverage areaQQ413 a is wirelessly connectable to the corresponding base stationQQ412 a. While a plurality of UEs QQ491, QQ492 are illustrated in thisexample, the disclosed embodiments are equally applicable to a situationwhere a sole UE is in the coverage area or where a sole UE is connectingto the corresponding base station QQ412.

Telecommunication network QQ410 is itself connected to host computerQQ430, which may be embodied in the hardware and/or software of astandalone server, a cloud-implemented server, a distributed server oras processing resources in a server farm. Host computer QQ430 may beunder the ownership or control of a service provider, or may be operatedby the service provider or on behalf of the service provider.Connections QQ421 and QQ422 between telecommunication network QQ410 andhost computer QQ430 may extend directly from core network QQ414 to hostcomputer QQ430 or may go via an optional intermediate network QQ420.Intermediate network QQ420 may be one of, or a combination of more thanone of, a public, private or hosted network; intermediate network QQ420,if any, may be a backbone network or the Internet; in particular,intermediate network QQ420 may comprise two or more sub-networks (notshown).

The communication system of FIG. 15 as a whole enables connectivitybetween the connected UEs QQ491, QQ492 and host computer QQ430. Theconnectivity may be described as an over-the-top (OTT) connection QQ450.Host computer QQ430 and the connected UEs QQ491, QQ492 are configured tocommunicate data and/or signalling via OTT connection QQ450, usingaccess network QQ411, core network QQ414, any intermediate network QQ420and possible further infrastructure (not shown) as intermediaries. OTTconnection QQ450 may be transparent in the sense that the participatingcommunication devices through which OTT connection QQ450 passes areunaware of routing of uplink and downlink communications. For example,base station QQ412 may not or need not be informed about the pastrouting of an incoming downlink communication with data originating fromhost computer QQ430 to be forwarded (e.g., handed over) to a connectedUE QQ491. Similarly, base station QQ412 need not be aware of the futurerouting of an outgoing uplink communication originating from the UEQQ491 towards the host computer QQ430.

FIG. 16: Host computer communicating via a base station with a userequipment over a partially wireless connection in accordance with someembodiments

Example implementations, in accordance with an embodiment, of the UE,base station and host computer discussed in the preceding paragraphswill now be described with reference to FIG. 16. In communication systemQQ500, host computer QQ510 comprises hardware QQ515 includingcommunication interface QQ516 configured to set up and maintain a wiredor wireless connection with an interface of a different communicationdevice of communication system QQ500. Host computer QQ510 furthercomprises processing circuitry QQ518, which may have storage and/orprocessing capabilities. In particular, processing circuitry QQ518 maycomprise one or more programmable processors, application-specificintegrated circuits, field programmable gate arrays or combinations ofthese (not shown) adapted to execute instructions. Host computer QQ510further comprises software QQ511, which is stored in or accessible byhost computer QQ510 and executable by processing circuitry QQ518.Software QQ511 includes host application QQ512. Host application QQ512may be operable to provide a service to a remote user, such as UE QQ530connecting via OTT connection QQ550 terminating at UE QQ530 and hostcomputer QQ510. In providing the service to the remote user, hostapplication QQ512 may provide user data which is transmitted using OTTconnection QQ550.

Communication system QQ500 further includes base station QQ520 providedin a telecommunication system and comprising hardware QQ525 enabling itto communicate with host computer QQ510 and with UE QQ530. HardwareQQ525 may include communication interface QQ526 for setting up andmaintaining a wired or wireless connection with an interface of adifferent communication device of communication system QQ500, as well asradio interface QQ527 for setting up and maintaining at least wirelessconnection QQ570 with UE QQ530 located in a coverage area (not shown inFIG. 16) served by base station QQ520. Communication interface QQ526 maybe configured to facilitate connection QQ560 to host computer QQ510.Connection QQ560 may be direct or it may pass through a core network(not shown in FIG. 16) of the telecommunication system and/or throughone or more intermediate networks outside the telecommunication system.In the embodiment shown, hardware QQ525 of base station QQ520 furtherincludes processing circuitry QQ528, which may comprise one or moreprogrammable processors, application-specific integrated circuits, fieldprogrammable gate arrays or combinations of these (not shown) adapted toexecute instructions. Base station QQ520 further has software QQ521stored internally or accessible via an external connection.

Communication system QQ500 further includes UE QQ530 already referredto. It's hardware QQ535 may include radio interface QQ537 configured toset up and maintain wireless connection QQ570 with a base stationserving a coverage area in which UE QQ530 is currently located. HardwareQQ535 of UE QQ530 further includes processing circuitry QQ538, which maycomprise one or more programmable processors, application-specificintegrated circuits, field programmable gate arrays or combinations ofthese (not shown) adapted to execute instructions. UE QQ530 furthercomprises software QQ531, which is stored in or accessible by UE QQ530and executable by processing circuitry QQ538. Software QQ531 includesclient application QQ532. Client application QQ532 may be operable toprovide a service to a human or non-human user via UE QQ530, with thesupport of host computer QQ510. In host computer QQ510, an executinghost application QQ512 may communicate with the executing clientapplication QQ532 via OTT connection QQ550 terminating at UE QQ530 andhost computer QQ510. In providing the service to the user, clientapplication QQ532 may receive request data from host application QQ512and provide user data in response to the request data. OTT connectionQQ550 may transfer both the request data and the user data. Clientapplication QQ532 may interact with the user to generate the user datathat it provides.

It is noted that host computer QQ510, base station QQ520 and UE QQ530illustrated in FIG. 16 may be similar or identical to host computerQQ430, one of base stations QQ412 a, QQ412 b, QQ412 c and one of UEsQQ491, QQ492 of FIG. 15, respectively. This is to say, the innerworkings of these entities may be as shown in FIG. 16 and independently,the surrounding network topology may be that of FIG. 15.

In FIG. 16, OTT connection QQ550 has been drawn abstractly to illustratethe communication between host computer QQ510 and UE QQ530 via basestation QQ520, without explicit reference to any intermediary devicesand the precise routing of messages via these devices. Networkinfrastructure may determine the routing, which it may be configured tohide from UE QQ530 or from the service provider operating host computerQQ510, or both. While OTT connection QQ550 is active, the networkinfrastructure may further take decisions by which it dynamicallychanges the routing (e.g., on the basis of load balancing considerationor reconfiguration of the network).

Wireless connection QQ570 between UE QQ530 and base station QQ520 is inaccordance with the teachings of the embodiments described throughoutthis disclosure. One or more of the various embodiments improve theperformance of OTT services provided to UE QQ530 using OTT connectionQQ550, in which wireless connection QQ570 forms the last segment. Moreprecisely, the teachings of these embodiments may improve the latencysince the SCG configuration of the UE is known and thereby providebenefits such as reduced waiting time and better responsiveness.

A measurement procedure may be provided for the purpose of monitoringdata rate, latency and other factors on which the one or moreembodiments improve. There may further be an optional networkfunctionality for reconfiguring OTT connection QQ550 between hostcomputer QQ510 and UE QQ530, in response to variations in themeasurement results. The measurement procedure and/or the networkfunctionality for reconfiguring OTT connection QQ550 may be implementedin software QQ511 and hardware QQ515 of host computer QQ510 or insoftware QQ531 and hardware QQ535 of UE QQ530, or both. In embodiments,sensors (not shown) may be deployed in or in association withcommunication devices through which OTT connection QQ550 passes; thesensors may participate in the measurement procedure by supplying valuesof the monitored quantities exemplified above, or supplying values ofother physical quantities from which software QQ511, QQ531 may computeor estimate the monitored quantities. The reconfiguring of OTTconnection QQ550 may include message format, retransmission settings,preferred routing etc.; the reconfiguring need not affect base stationQQ520, and it may be unknown or imperceptible to base station QQ520.Such procedures and functionalities may be known and practiced in theart. In certain embodiments, measurements may involve proprietary UEsignalling facilitating host computer QQ510′s measurements ofthroughput, propagation times, latency and the like. The measurementsmay be implemented in that software QQ511 and QQ531 causes messages tobe transmitted, in particular empty or ‘dummy’ messages, using OTTconnection QQ550 while it monitors propagation times, errors etc.

FIG. 17: Methods implemented in a communication system including a hostcomputer, a base station and a user equipment in accordance with someembodiments.

FIG. 17 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station and a UEwhich may be those described with reference to FIGS. 15 and 16. Forsimplicity of the present disclosure, only drawing references to FIG. 17will be included in this section. In step QQ610, the host computerprovides user data. In substep QQ611 (which may be optional) of stepQQ610, the host computer provides the user data by executing a hostapplication. In step QQ620, the host computer initiates a transmissioncarrying the user data to the UE. In step QQ630 (which may be optional),the base station transmits to the UE the user data which was carried inthe transmission that the host computer initiated, in accordance withthe teachings of the embodiments described throughout this disclosure.In step QQ640 (which may also be optional), the UE executes a clientapplication associated with the host application executed by the hostcomputer.

FIG. 18: Methods implemented in a communication system including a hostcomputer, a base station and a user equipment in accordance with someembodiments.

FIG. 18 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station and a UEwhich may be those described with reference to FIGS. 15 and 16. Forsimplicity of the present disclosure, only drawing references to FIG. 18will be included in this section. In step QQ710 of the method, the hostcomputer provides user data. In an optional substep (not shown) the hostcomputer provides the user data by executing a host application. In stepQQ720, the host computer initiates a transmission carrying the user datato the UE. The transmission may pass via the base station, in accordancewith the teachings of the embodiments described throughout thisdisclosure. In step QQ730 (which may be optional), the UE receives theuser data carried in the transmission.

FIG. 19: Methods implemented in a communication system including a hostcomputer, a base station and a user equipment in accordance with someembodiments

FIG. 19 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station and a UEwhich may be those described with reference to FIGS. 15 and 16. Forsimplicity of the present disclosure, only drawing references to FIG. 19will be included in this section. In step QQ810 (which may be optional),the UE receives input data provided by the host computer. Additionallyor alternatively, in step QQ820, the UE provides user data. In substepQQ821 (which may be optional) of step QQ820, the UE provides the userdata by executing a client application. In substep QQ811 (which may beoptional) of step QQ810, the UE executes a client application whichprovides the user data in reaction to the received input data providedby the host computer. In providing the user data, the executed clientapplication may further consider user input received from the user.Regardless of the specific manner in which the user data was provided,the UE initiates, in substep QQ830 (which may be optional), transmissionof the user data to the host computer. In step QQ840 of the method, thehost computer receives the user data transmitted from the UE, inaccordance with the teachings of the embodiments described throughoutthis disclosure.

FIG. 20: Methods implemented in a communication system including a hostcomputer, a base station and a user equipment in accordance with someembodiments

FIG. 20 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station and a UEwhich may be those described with reference to FIGS. 15 and 16. Forsimplicity of the present disclosure, only drawing references to FIG. 20will be included in this section. In step QQ910 (which may be optional),in accordance with the teachings of the embodiments described throughoutthis disclosure, the base station receives user data from the UE. Instep QQ920 (which may be optional), the base station initiatestransmission of the received user data to the host computer. In stepQQ930 (which may be optional), the host computer receives the user datacarried in the transmission initiated by the base station.

Any appropriate steps, methods, features, functions, or benefitsdisclosed herein may be performed through one or more functional unitsor modules of one or more virtual apparatuses. Each virtual apparatusmay comprise a number of these functional units. These functional unitsmay be implemented via processing circuitry, which may include one ormore microprocessor or microcontrollers, as well as other digitalhardware, which may include digital signal processors (DSPs),special-purpose digital logic, and the like. The processing circuitrymay be configured to execute program code stored in memory, which mayinclude one or several types of memory such as read-only memory (ROM),random-access memory (RAM), cache memory, flash memory devices, opticalstorage devices, etc. Program code stored in memory includes programinstructions for executing one or more telecommunications and/or datacommunications protocols as well as instructions for carrying out one ormore of the techniques described herein. In some implementations, theprocessing circuitry may be used to cause the respective functional unitor circuits to perform corresponding functions according one or moreembodiments of the present disclosure.

Modifications and other embodiments of the disclosed embodiments willcome to mind to one skilled in the art having the benefit of theteachings presented in the foregoing descriptions and the associateddrawings. Therefore, it is to be understood that the embodiment(s)is/are not to be limited to the specific embodiments disclosed and thatmodifications and other embodiments are intended to be included withinthe scope of this disclosure. Although specific terms may be employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation.

ABBREVIATIONS

At least some of the following abbreviations may be used in thisdisclosure. If there is an inconsistency between abbreviations,preference should be given to how it is used above. If listed multipletimes below, the first listing should be preferred over any subsequentlisting(s).

ACK Acknowledgement

AP Application Protocol

BSR Buffer Status Report

CE Control Element

CP Control Plane

DC Dual Connectivity

DCI Downlink Control Information

DL Downlink

DRB Data Radio Bearer

eNB (EUTRAN) base station

E-RAB EUTRAN Radio Access Bearer

FDD Frequency Division Duplex

gNB NR base station

GTP-UGPRS Tunneling Protocol-User Plane

IP Internet Protocol

LTE Long Term Evolution

MCG Master Cell Group

MAC Medium Access Control

MeNB Master eNB

MgNB Master gNB

MN Master Node

NACK Negative Acknowledgement

NR New Radio

PDCP Packet Data Convergence Protocol

PUSCH Physical Uplink Shared Channel

RLC Radio Link Control

RLF Radio Link Failure

RRC Radio Resource Control

SCG Secondary Cell Group

SCTP Stream Control Transmission Protocol

SeNB Secondary eNB

S-SgNB Source Secondary gNB

SgNB Secondary gNB

SN Secondary Node

S-SN Source Secondary Node

SR Scheduling Request

SRB Signalling Radio Bearer

TDD Time Division Duplex

TEID Tunnel Endpoint IDentifier

TNL Transport Network Layer

T-SgNB Target Secondary gNB

T-SN Target Secondary Node

UCI Uplink Control Information

UDP User Datagram Protocol

UE User Equipment

UL Uplink

UP User Plane

URLLC Ultra Reliable Low Latency Communication

X2 Interface between base stations

What is claimed is:
 1. A method performed by a user equipment, UE, forhandling communication in a wireless communication network, providingdual connectivity, DC, communication through a master node using amaster cell group, MCG, over a first radio interface between the UE andthe master node and through a secondary node using a secondary cellgroup, SCG, over a second radio interface between the UE and thesecondary node, the first radio interface using a first radio accesstechnology and the second radio interface using a second radio accesstechnology that is different from the first radio access technology, themethod comprising: detecting a failure associated with the SCG;suspending SCG transmission over an SCG link; performing areconfiguration of the SCG upon reception of an SCG radio resourcecontrol, RRC, message with SCG configuration, the SCG RRC message beingembedded in an MCG radio resource control, RRC, message, from the masternode; if the embedded SCG RRC message contains mobility information forthe SCG link, resuming the SCG transmission over the SCG link; and ifthe embedded SCG RRC message does not contain mobility information forthe SCG link, not resuming the SCG transmission.
 2. The method accordingto claim 1, wherein performing the reconfiguration of SCG comprisesapplying the reconfiguration based on whether the UE has started totransmit a RRC complete message.
 3. The method according to claim 2,wherein performing the reconfiguration of SCG configuration comprisessending an RRC complete message one of: in an RRC message for the SCGdirectly to the secondary node; and embedded within an RRC message tothe master node.
 4. The method according to claim 1, wherein performingthe reconfiguration of SCG configuration comprises sending an RRCcomplete message one of: in an RRC message for the SCG directly to thesecondary node; and embedded within an RRC message to the master node.5. A method performed by a secondary node for handling communication ofa user equipment, UE, in a wireless communication network, the secondarynode being configured to operate in cooperation with a master node toprovide dual connectivity, DC, communication with the user equipmentthrough the secondary node using a secondary cell group, SCG, over asecond radio interface between the UE and the secondary node and themaster node using a master cell group, MCG, over a first radio interfacebetween the UE and the master node, the first radio interface using afirst radio access technology and the second radio interface using asecond radio access technology that is different from the first radioaccess technology, the method comprising transmitting to the master nodein an X2 message, a mobility flag indicating to the master node if anSCG reconfiguration message sent to the UE from the secondary nodeembedded within a MCG RRC message contains mobility information for theSCG link, such that the mobility flag is set to true when the SCGreconfiguration message contains mobility information and the mobilityflag is one of set to false and absent when the SCG reconfigurationmessage does not contain mobility information.
 6. A user equipment, UE,for handling communication in a wireless communication network providingdual connectivity, DC, communication through a master node using amaster cell group, MCG, over a first radio interface between the UE andthe master node and through a secondary node using a secondary cellgroup, SCG, over a second radio interface between the UE and thesecondary node, the first radio interface using a first radio accesstechnology and the second radio interface using a second radio accesstechnology that is different from the first radio access technology, theUE being configured to: detect a failure associated with the SCG suspendSCG transmission over an SCG link; and perform a reconfiguration of theSCG upon reception of an SCG radio resource control, RRC, message withSCG configuration, said SCG RRC message being embedded in an MCG radioresource control, RRC, message, from the master node; if the embeddedSCG RRC message contains mobility information for the SCG link, resumingthe SCG transmission over the SCG link; and if the embedded SCG RRCmessage does not contain mobility information for the SCG link, notresuming the SCG transmission.
 7. The UE according to claim 6, whereinthe UE is configured to perform the reconfiguration of SCG by applyingthe reconfiguration based on whether the UE has started to transmit aRRC complete message.
 8. The UE according to claim 7, wherein the UE isconfigured to perform the reconfiguration of the SCG by being configuredto send an RRC complete message in an RRC message for the SCG one of:directly to the secondary node; and embedded within an RRC message tothe master node.
 9. The UE according to claim 6, wherein the UE isconfigured to perform the reconfiguration of the SCG by being configuredto send an RRC complete message in an RRC message for the SCG one of:directly to the secondary node; and embedded within an RRC message tothe master node.
 10. A secondary node for handling communication of auser equipment, UE, in a wireless communication network, wherein thesecondary node is configured to operate in cooperation with a masternode to provide dual connectivity, DC, communication with the userequipment through the secondary node using a secondary cell group, SCG,over a second radio interface between the UE and the secondary node andthe master node using a master cell group, MCG, over a first radiointerface between the UE and the master node, the first radio interfaceusing a first radio access technology and the second radio interfaceusing a second radio access technology that is different from the firstradio access technology wherein the secondary node is configured to:transmit, to the master node in an X2 message, a mobility flagindicating to the master node if an SCG reconfiguration message sent tothe UE from the secondary node embedded within a MCG RRC messagecontains mobility information for the SCG link, such that the mobilityflag is set to true when the SCG reconfiguration message containsmobility information and the mobility flag set to false is absent whenthe SCG reconfiguration message does not contain mobility information.